The present invention relates to a fuel injection valve for an internal combustion engine.
In the field of gasoline engines, such as for automobiles, a system in which a fuel injection valve, such as a solenoid valve, is driven by an electrical signal to inject fuel into a intake passage has been employed.
In connection with these kinds of fuel injection valves, measures for atomizing fuel, such as by swirling the fuel and injecting the same in thin films or by introducing air into a nozzle body of a fuel injection valve and joining the air flow with a swirling fuel after injection, have been proposed as disclosed, for example, in JP-A-57-183559(1982) and JP-A-64-24161(1989).
However, in the conventional art, when atomizing the swirling fuel after injection with the air flow, as indicated above, no special measures were taken to limit the amount of air for atomization introduced into the nozzle body. In particular, such as during an idling operation wherein a small amount of fuel is required, a relatively large amount of air tends to be supplied for the atomization, with the result that the amount of air passing through the throttle valve in the intake air passage when the throttle valve is fully closed has to be extremely limited.
In order to reduce the clearance area of the throttle valve when the same is fully closed, the production accuracy of the throttle valve has to be further enhanced, but this is practically difficult in view of the production cost.
Further, the moving speed of atomized fuel droplets injected from the fuel injection valve is as high as about 20 m/s, so that injected fuel which impacts on an intake pipe wall and/or an intake valve tends to form a liquid film thereon which limits improvement of the fuel atomization.